Presently, pharmacy and medicine provide delivery systems for the constant-rate delivery of a drug to a drug-recipient user. The prior art provides infusion pumps as disclosed by Perry, Carpenter and Griesenger in U.S. Pat. No. 4,318,400, oral matrix systems as disclosed by Urquhart and Theeuwes in U.S. Pat. No. 4,863,744, osmotic systems as patented by Theeuwes and Higuchi in U.S. Pat. Nos. 3,845,770 and 3,916,899, osmopolymer-powered systems as provided by Wong, Barclay, Deters and Theeuwes in U.S. Pat. No. 4,783,337, and implants as presented by Choi and Heller in U.S. Pat. No. 4,093,709, for constant-rate delivery of a drug of the longest duration consistent with reproducible therapeutic results.
While these prior art delivery systems provide good therapy and achieve their intended results there are however, some therapeutic programs that require the dose of drug be administered in time-varying patterns of delivery. The time-varying patterns of drug delivery include (1) a drug-free interval followed by drug pulses of various duration for extended periods of time, (2) an immediate drug does followed by a drug-free interval followed by a drug-delivery period, and (3) a single dose followed by a delayed dose for optimum therapy, and like patterns of drug delivery.
For example, it is known, in Chronobiologia, Vol. 13, pages 239 to 243, (1986), that blood pressure has within-day rhythmicity, and that the highest pressure values are seen often in the morning hours just after waking by the patient. The rise in blood pressure occurring at waking requires a dosage form that is administered on retiring and delivers its drug after a drug-free interval during sleep. This drug delivery pattern provides the need for therapy at the appropriate time, thereby substantially lessening the incidence of a waking elevated blood pressure. Presently a dosage form is unavailable to fulfill this need. It is self-evident from the above presentation that a critical and presently unfilled need exists for a delivery system that can delivery a dose of drug in a time-varying pattern of delivery. The need exits for a programmable delivery system that can provide a desired time-profile of drug administration to achieve the intended and therapeutic effect.